Human T-cell lymphotropic virus-III (HTLV-III) is almost certainly the causal agent of the epidermic human disease Acquired Immunodeficiency Syndrome (AIDS). AIDS is a major health problem in the U.S. and an effective means of preventing the spread of the disease would be of great value. This proposal focuses on interrupting the cycle of viral replication and expression of viral antigens in individuals exposed to or already infected with the virus. Syntro Corporation, using recombinant DNA technology, has developed proprietary methods for the delivery to and expression of gnes in animals to produce effective vaccines. In Phase I of the proposal, this technology will be applied to construct genes which, upon expression, should block the replication of HTLV-III in T-cel lymphocytes. In Phase II, these constructs will be placed in the appropriate delivery system and tested for efficacy.